This invention relates generally to junction devices and more particularly to junction arrays for superconducting and non superconducting applications.
Recent technological advances have made it possible to form very fine diffraction gratings on photoresists by optical interference of the two laser beams. These advances have found limited application in thin-film distributed feedback lasers and microwave acoustic waves. Related advances, involving fabrication of gratings with positive photo-resists in which the exposing and developing processes are carried out simultaneously, create gratings with relatively deep grooves and sharp ridges.
Most interest in junction arrays concerns their application to the superconducting state. Super-current has been known and investigated for some time, however the discovery of the Josephson effect has stimulated interest as of late. The effect relates to current flow through a discontinuance separating two superconductive regions. Termed a, "weak link" the region of discontinuance is anything which separates two superconductive regions and which is not itself a superconductor. This would include a potential superconductor not in a superconductive state as are the connecting superconductive regions, but which nevertheless transfers current therebetween. The weak link may be, for example, a layer of insulator, or a layer of non-superconductive metal or semiconductor material or several layers, some of which may be superconductive (see "Superconductivity", R. D. Parks, Volumes 1 and 2, Marcel Dekker Inc. New York 1969).
Both theoretical and experimental results have shown that multiple Josephson junctions can be made to self-synchronize and enter a "super-radiant" state by interaction with an electromagnetic cavity or an external rf electromagnetic field. Consequently, the radiation generated by an array of Josephson junctions should increase as M.sup.2, where M is the number of junctions in the array. Likewise, when the junctions are used as detectors, the detection sensitivity of an array will also increase as M.sup.2.
Although multiple Josephson junctions have been made previously with granular films, compressed aluminum powder and Nobium balls the physical dimension of the junctions in each case is nonuniform and the spacing between junctions is uncontrollable. The devices presented hereinafter in contrast to the known art are carefully controlled in spacing and junction dimension.
For non-superconducting junctions, the use of metal to metal point contact as detector, mixer and generator of infrared radiation is seen as a substantial advancement in the art. It is further seen where the use of an array will now only improve the sensitivity but also give rise to directivity of point-contact junctions. The ability of fabricating uniformly spaced junctions for point-contact applications will result in a substantial reduction in size and cost of currently available devices and the discovery of uses as well.